Bichromatic optical imaging is proposed for in-vivo detection and imaging through biological tissue. A major application is clinical optical mammographic screening for breast cancer. Unlike conventional x-ray mammography, the proposed optical imaging technique utilizes visible or near-infrared radiation. Since this non-ionizing radiation poses no risk of radiation-induced carcinoma, bichromatic optical breast-cancer screening examinations can be repeated periodically with no risk to the patient--a revolutionary development. Bichromatic imaging utilizes an array of light sources, each of which contains at least two wavelength components that are temporally correlated with one another. The presence of lesions, whose absorption and/or scattering properties differ from those of the surrounding tissue, can be determined from observation of the light transmitted through the tissue. Scans of duration 1 sec will be adequate to detect mm-size lesions in a 40-mm-thick breast. Phase I is a theoretical effort to assess the feasibility of the technique and design a Phase II proof-of-principle laboratory demonstration.